Additive manufacturing as a new manufacturing technology has significant advantages in producing complex impeller parts, but the surface roughness limits its wide application. Therefore, the work aims to solve the problem of excessive surface roughness of TC4 titanium alloy (Ti6Al4V) impeller parts produced by additive manufacturing. In order to improve the surface roughness of through-hole or complex outer surface parts caused by powder adhesion and spheroidization defects, abrasive flow polishing technology was applied to polish the surface of TC4 titanium alloy specimens. The effect of abrasive flow polishing on the surface roughness and morphology of TC4 titanium alloy was studied under different abrasive particle size, working pressure and processing time. The polishing process of abrasive was simulated by Fluent software to explore the mechanism of abrasive particles on the static pressure, dynamic pressure, turbulent kinetic energy and turbulence intensity near the wall. A three-dimensional impeller model was built and the actual processing conditions were taken as simulation parameters to verify the effectiveness of abrasive flow polishing method. At the same time, wear resistance of the TC4 titanium alloy before and after abrasive flow polishing were tested and analyzed. The TC4 titanium alloy specimens produced by additive manufacturing were cut into 40 mm×40 mm×5 mm by wire cutting, cleaned and dried. The SMK-600 abrasive flow polishing machine was used to optimize the surface roughness of titanium alloy specimens by cutting the workpiece surface through the reciprocating movement of abrasive media. The solid particles of abrasive medium were SiC abrasive particles, and the mixture of methyl silicone oil and polyacrylamide was used as liquid medium. Experiments verified that titanium alloy parts with surface roughness Ra<2.5 μm were obtained when the abrasive grain size was 0.425 mm, the processing pressure was 9 MPa and the polishing time was 20 min, meeting the processing requirements. The friction and wear test results demonstrated that the friction coefficient of TC4 titanium alloy specimen surface decreased from 0.428 1 before abrasive flow polishing to 0.385 3 after polishing, and the reduction of friction coefficient represented the improvement of wear resistance. The wear mechanism was changed from adhesive wear and spalling wear to abrasive wear. The reciprocating movement of the abrasive in the process of abrasive flow polishing caused plastic deformation of the material surface, which resulted in changes in work-hardened and the grains were refined, thus effectively improving the wear resistance. Numerical simulation results indicated that the blade spacing gradually increased as the abrasive fluid moved from top to bottom, the dynamic pressure, turbulent kinetic energy and turbulence intensity on the surface of the impeller gradually weaken. When the fluid reached the bottom of the impeller, the dynamic pressure, turbulence strength and turbulence kinetic energy increased due to the role of the restraint device. Therefore, the polishing effect of upper and lower ends of the blade were better than those at the middle part. In the process of abrasive flow polishing, the surface of the specimen is work-hardened due to plastic deformation, and the grains are refined, thus effectively improving the wear resistance. The abrasive flow polishing is suitable for improving the surface quality of complex outer surface parts such as impeller. The effectiveness of abrasive flow polishing technology for complex curved surfaces is verified by numerical simulation and experimental analysis, which provides a theoretical basis for abrasive flow polishing technology.